How Do I Permanently Crop a PDF?

Why doesn't cropping delete the trimmed part?

Cropping a PDF changes its CropBox, the box that tells a reader which part of the page to show. The page's full content stays stored in its MediaBox, untouched.

• MediaBox is the whole sheet: the PDF format (ISO 32000-1:2008, section 14.11.2) treats it as the one page box every page must have.
• CropBox is just a viewing window: it holds four numbers, and when it's missing, a reader falls back to showing the whole MediaBox instead.
• Adobe says so directly: Acrobat's own help page for cropping states that trimming a page doesn't shrink the file, because the cut area is hidden, not removed.
• Nothing is redrawn: cropping edits a rectangle of coordinates. It never touches the text or images already on the page.

How can the hidden part come back?

It can come back through ordinary steps, because the content behind a crop never actually left the file.

• Undo the crop: opening the crop tool again and dragging the handles back out restores the full page in most editors.
• Open it elsewhere: some PDF readers and code libraries look at the MediaBox and ignore the CropBox, so they show the page in full, trimmed part included.
• Pull the text out: a script or a word processor that reads text from the whole page can still find words sitting outside the visible crop.

How do I crop a PDF for good?

Trim the margins first, then flatten the page so only the kept area is ever drawn again.

• Crop it: Crop PDF sets new margins on the pages you choose, by an equal amount on every edge.
• Flatten it: Flatten PDF redraws each page as a picture, at 150 dots per inch by default, using only what sits inside the crop. Nothing outside it gets drawn, so it can't be read back.
• Check it: open the result and try to select text near the old edge. If there's nothing there, the trim held.
• On a phone: some apps, like Xodo, add a direct "save a permanently cropped copy" option right after you crop, so you don't need a second step.

Is there a way to crop for good without turning pages into pictures?

Yes, a couple of tools can cut the hidden part away while keeping the text as text, though each works a little differently.

• mutool trim: this free command line tool from the MuPDF project cuts a page down to its CropBox, or any other page box, instead of just hiding what sits outside it.
• Acrobat's Preflight panel: its fixups can permanently remove whatever falls outside a page's trim and bleed boxes, from inside Acrobat Pro.
• Printing to a new PDF: sending the file through a PDF printer bakes the crop in, since the printer only sees the visible page. This usually turns the text into a picture too.

Can I use cropping to hide something sensitive?

No. Cropping only hides content from view, it never deletes it, so it can't stand in for redaction.

• For a name, a number or a photo that must not come back, use Redact PDF, which deletes the text and blanks the pixels in the area you mark.
• Cropping is for layout, not privacy: use it for scanner edges, a blank margin or a header you want gone from view, never for personal or confidential details.

Try the tools

Try it on your own file. The tools are free and you don't need an account.